This invention relates to apparatus for data transfer with a rotating magnetic disk, particularly a flexible magnetic disk, which is normally packaged in cartridge form. More particularly, the invention pertains to a system for saving power consumed by a sensor or sensors incorporated in such rotating disk data storage apparatus.
Various power saving schemes have been suggested and used with floppy disk drives. Among such conventional suggestions is that described and claimed in U.S. Pat. No. 4,658,307 filed by Tsuyuguchi et al. and assigned to the assignee of the instant application. Tsuyuguchi et al. teaches to connect the disk motor drive circuit, the head motor drive circuit, and the read/write circuit, all standard components of the disk drive, to a power supply via a power saving switch. This switch is closed only when the floppy disk cartridge is loaded in the disk drive. The motor drive circuits and read/write circuit are therefore not powered in the absence of the disk cartridge, even if the complete data processing system, comprising a host and one or more disk drives, is powered on. A very substantial saving of power can thus be accomplished.
As far as the applicant is aware, however, various sensors customarily incorporated in disk drives were conventionally held powered even when the disk drive was standing by, that is, when the associated drive select signal was not commanding the operation of that disk drive. Such sensors include a file protect sensor for sensing whether the loaded disk cartridge is protected against erasure or writing, a disk capacity sensor for discriminating between one-megabyte and two-megabyte disk, and another disk capacity sensor for discriminating between four-megabyte and other capacity disks.
Admittedly, the sensors and associated circuitry demand no inordinately large power, the current flowing through each sensor being one milliampere or so. However, now that the power requirements of other power consuming parts of the disk drive have been reduced to a minimum, the saving of power consumed by the sensors has become imperative in view of strong, consistent demands from the users for less power consuming disk drives.